Abstract: An attachment for automatically forming a horizontal thread loop over the sewing area of a sewing machine to enable the loop to be sewn onto a garment as a belt loop includes a prong mounted on one side of the sewing area. A solenoid driven linkage located on the other side of sewing area carries an eye which receives thread from a source. The free end of the thread, after passage through the eye is pinched initially between a fixed sleeve and a moving arrow-shaped blade carried for movement with a sliding bed plate of the machine and located on the other side of the sewing area. In response to brief energization of the solenoid, the eye is carried across the sewing area and about the prong to catch the thread thereon and thereby form a loop having two straight crossing segments radiating from the prong respectively to the eye and the sleeve.